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Unit 6

Unit 6. Memory. ROM and RAM. Read Only Memory-holds data when power is turned off. (BIOS chip is ROM) Random Access Memory- losses data when power is turned off. RAM ROM. Static RAM and Dynamic RAM. Dynamic RAM uses capacitors. needs refreshing to hold data.

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Unit 6

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  1. Unit 6 Memory

  2. ROM and RAM • Read Only Memory-holds data when power is turned off. (BIOS chip is ROM) • Random Access Memory- losses data when power is turned off. RAM ROM

  3. Static RAM and Dynamic RAM • Dynamic RAM uses capacitors. • needs refreshing to hold data. • Cheaper Per bit • Static RAM uses “Flip-Flops” doesn’t need refreshing. • easier to use • Faster • More expensive per bit • Smaller sizes

  4. Memory Caching • Data that the CPU uses often is saved in a small, fast memory location called Cache. • Cache controller tried to “guess” what data will be used next. • About 90% correct in guessing, so it is effective. • L1 cache is inside CPU, L2 cache is external.

  5. Error Checking and Parity • Number of high bits (1s) is counted. • An extra bit is added to the string to make the total number of high bits even or odd. • String is tested at other end to see if string is even or odd. • Parity must be set for even or odd at both ends of data path.

  6. Memory Technologies • Conventional • Fast page (FPM) • Extended Data out (EDO) • Burst EDO (BEDO) • Synchronous DRAM (SDRAM) • DDR (Double Data Rate) SDRAM • Rambus DRAM (RDRAM) • DDR2

  7. CAS Latency and RAS Latency • Column access strobe • Row Access Strobe • Refers to number of clock cycles it takes to read a row or column of data. • CAS is used more than RAS • CL2 is faster than CL3 • Use what mother board Mfr. recommends

  8. Memory Speed • Measured in MHz or nanoseconds • How much memory is installed • The type of technology used • The CL rating (lower the better) • ECC/parity or non-ECC/Nonparity • Non-ECC or nonparity is faster

  9. What to look for when buying memory • Buy largest and fasted your motherboard can support/you can afford • Tin or gold. Either is fine, just don’t mix and match as they will corrode due to reaction between metals • Will new memory be compatible with existing memory? • How many memory slots do I have. • What type of memory will my motherboard support?

  10. Installing RAM Locate the RAM sockets on motherboard

  11. Installing Memory Look for notches on RAM and in memory slot.

  12. Installing Memory Push firmly, but do not force the RAM into the socket.

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